Electric compressed-gas circuit breaker

ABSTRACT

An electric compressed-gas circuit breaker is disclosed and has two stationary contact pieces. A switching unit is movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position. The switching unit includes a supporting body and electrical insulation made of elastic, yielding material is disposed at the supporting body. A slide-contact ring is carried by the supporting body and slideably contacts one of the contact pieces in the closed position. The slide-contact ring is made of arcresistant material and is tension-fixed in the electrical insulation. The insulation is disposed between the supporting body and the ring thereby insulating the ring from the body. The slide-contact ring is configured at least in part as a body of carbon material. A plurality of elongated contact elements are disposed in the supporting body for electrically connecting the contact pieces when the switching unit is in the closed position and are in electrically conductive contact with the slide-contact ring when the ring and the contact elements are separated from the one contact piece when the switching unit moves into the open position.

United States Patent 1191 Handke 1 ELECTRIC COMPRESSED-GAS CIRCUIT BREAKER [75] Inventor: Siegfried Handke, Berlin, Germany [73] Assignee: Siemens Aktie ngeselscha ft,

Munich, Germany 22 Filed: Apr. 5, 1973 21 Appl. No.1 348,276

[30] Foreign Application Priority Data Apr. 25, 1972 Germany 2220897 52 U.S. c1 200/148 R [51] Int. Cl. [58] Field of Search H0lh 33/80 200/148 R, 148 B Primary Examiner-R0bert S. Macon Attorney, Agent, or Firm l(enyon & Kenyon Reilly Carr & Chapin [451 Dec. 10, 1974 57 ABSTRACT An electric compressed-gas circuit breaker is disclosed and has two stationary contact pieces. A switching unit is movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position. The switching unit includes a supporting body and electrical insulation made of elastic, yielding material is disposed at the supporting body. A slide-contact ring is carried by the supporting body and slideably contacts one of the contact pieces in the closed position. The slidecontact ring is made of arc-resistant material and is tension-fixed in the electrical insulation. The insulation is disposed between the supporting body and the ring thereby insulating the ring from the body. The slide-contact ring is configured at least in part as a body of carbon material. A plurality of elongated 6 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The invention relates to an electric compressed-gas circuit breaker having a blasting device consisting of a piston and a cylinder. Such a circuit breaker is described in the earlier filed U.S. Pat. application, Ser. No. 334,934, filed on Feb. 22, 1973 with the title: Electric Compressed-Gas Circuit Breaker; this type of breake'r has two nozzle-shaped stationary contacts and a bridging contact member connecting the contacts when the breaker is closed. The bridging contact member is equipped with a slide-contact ring of arc-resistant material and spring-loaded contact elements. For improving the commutation of the arc during the switching motion, the above-mentioned patent application teaches that the bridging contact member carries the slide-contact ring with electrical insulation interposed and that the slide-contact ring and the contact elements are electrically connected with each other at their separation from one of the stationary contacts.

It is desirable to obtain improved conditions during the time that the arc burns because it is then possible to hold both damage of the contacts and the formation of decomposition products to a minimum.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide an electric compressed-gas electric circuit breaker with which the foregoing improvements are obtained. The invention is an improvement over the circuit breaker disclosed in the above-mentioned earlier filed application.

The invention provides that the electrical insulation disposed between the supporting body and the contact ring be made of elastic, yielding material. Further, the slide-contact ring is at least partially a carbon structure, in particular a graphite structure, which is clamped in theelectrical insulation. With the use of carbon structures, particularly graphite structures, better conditions are obtained during the time that the arc burns because the destruction of the contacts and the formation of decomposition products due to the action of the arc can be kept very small.

The electric compressed-gas circuit breaker according to the invention includes: two stationary contact pieces; a switching unit movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position whereby electrically connecting the contact pieces when the switching unit is in the closed position and spring means spring load the contact elements to displace the same into electrically conductive contact with the slide-contact ring as the ring and the contact elements separate from the one contact piece when the switching unit moves into the open position.

Deutsche 'Auslegungsschrift 1,154,548 discloses graphite electrodes in electric circuit breakers employing an electro-negative gas containing fluorine, expecially, as an arc-quenching agent. The advantages obtainable in connection with the use of graphite structures mentioned there are fully retained in the present invention. In addition, the construction of the electric compressed-gas circuit breaker assumed in the invention makes it necessary that the graphite structure be in the form of a ring. Such graphite rings are more difficult to connect electrically and mechanically with the switching contacts than compact graphite electrodes.

The invention discloses that it is possible to clamp the slide-contact ring in the electric insulation and, because the insulation consists of an elastic, yielding material,'the ring can be held without excessive compression stresses in a mechanically secure manner. The ring is configuredas a carbon body, particularly, a graphite body. In this manner, an especially simple friction seal is obtained between the slide-contact ring and the electrically insulating material which carries it. The insulating material is mechanically stable over a wide temperature range. In the operating temperature range, any

7 changes in the dimensions of the graphite structure are an arc develops when the switching unit is moved to the 7 open position; and gas-blast means for blasting a stream of gas through the are when the switching unit is moved to the open position. The switching unit includes a supporting body, electrical insulation disposed at the suptaken up by the insulating material.

According to a subsidiary embodiment of the invention, the carbon structure is mounted friction-tight in a metallic sleeve and the sleeve is supported in the electrical insulation. The metallic sleeve can be advantageously coupled to the contact elements. In a further embodiment of the invention, the electrical insulation is made of polytetrafluoroethylene.

The invention makes it possible to construct an electric compressed-gas circuit breaker wherein the slidecontact ring of arc-resistant material carried by the ring of insulating material results in only slight burn-off during the arcing time and wherein a correspondingly low decomposition of the gaseous quenching and insulating medium occurs. In addition, configuring the slidecontact ring of a carbon structure affords further advantages because of its good lubricating properties. The carbon structure is preferably a graphite body.

Although the invention is illustrated and described herein as an electric compressed-gas circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram, in longitudinal section, of an electric compressed-gas circuit breaker according to the invention. The left-half of the diagram shows the switching unit in the open position and the right half, theclosed position.

FIG. 2 illustrates details of the contact arrangement used in the circuit breaker of FIG. 1.

FIG. -3 illustrates an alternate embodiment of the contact arrangement for the circuit breaker of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The high-voltage circuit breaker of FIG. 1 can be operated, for example, at 1 kV and can use sulfur hexafluoride as the quenching and insulating medium. In order to more clearly depict the portions of the breaker pertinent to the invention, only those parts which are necessary for understanding the invention are shown. The parts of the circuit breaker which are at ground potential, the actuator and the standoff insulators are not illustrated. The electric circuit breaker is constructed as a compressed-gas breaker and has a switching chamber l which consists, for example, of porcelain and supports at its upper end a connecting member, not shown in detail. A hollow metallic body 2 is attached to this connecting member. The body 2 protrudes into the interior of the switching chamber 1 and carries a stationary contact 3. Opposite the contact 3 is a stationary contact 4. Both contacts 3 and 4 are made hollow to carry away the switching gases and are configured as nozzles'at their respective end faces disposed opposite each other.

In the closed position, the two stationary contacts 3 and 4 are connected by a switching unit in the form of a bridging contact member 6 having a tubular configuration. Spring-loaded elongated elements 7 are disposed inside contact member 6 and have contact areas 8 which are pushed against the stationary contacts 3 and 4 with a predetermined contact pressure. The bridging contact member 6 carries a slide-contact ring 9 of arc-resistant, electrically conductive material with electrical insulation 10 interposed. The special configuration of the insulation and the slide-contact ring is explained in greater detail below with reference to FIGS. 2 and 3. I

The tubular bridging contact member 6 is screwed into a-coupling member 18 which in turn is connected via fastening elements 19 with a tube 20 of insulating material. The tube 20 constitutes a blast cylinder.

On its face 21, the blast cylinder carries a nozzleshaped body which surrounds the stationary contact 3.

The insulating tube 20, for example, is made of one piece of material such as fiber-reinforced plastic. During the opening motion, the insulating tube 20 is pulled, together with the bridging contact member 6, over a relatively stationary piston 24, so that a quenching medium flow is prepared. Tie rods 12 engage the coupling member 18 and are pivotally supported at a pin 13. A drive member (not shown in detail) is coupled to the tie rods 12 and moves the breaker from the closed position shown to the right of the center line to the open position shown to the left.

The switching chamber 1 is completely filled with sulfur hexafluoride at a pressure of, for example, 4 bar. When the breaker opens, the contact member 6, together with the tube 20, moves from the top to the bottom. The sulfur hexafluoride inside the tube 20 is com pressed in this process because it cannot yet flow out at the beginning of the opening motion. Only when the tube 20 has travelled a definite stroke do the contact elements 7 of the bridging contact member 6 and the contact ring 9 slide off the stationary contact 3, so that with the metallic separation a discharge clearance is created. The sulfur hexafluoride, compressed up to this point to approximately 16 bars, flows through the discharge clearance to the discharge nozzles which are formed by the two stationary contacts 3 and 4. The arc is commutated here from the contact ring 9 to the burn-off electrodes made of arc-resistant material provided at the contact 4 and is quenched because of the favorable flow conditions which prevail at the nozzles.

In the open position the gap between the contacts 3 and 4 is free. The field strength there is low because the contacts, being electrodes of large area, produce a uniform field.

FIG. 2 shows the upper-half of a longitudinal section of a contact arrangement for the electric compressedgas circuit breaker of FIG. 1. The same parts are designated by the same reference symbols as in FIG. 1. The electric insulation 10 consists of an elastic, yielding material such as polytetrafluoroethylene or the like whereas the slide-contact ring 9 is a carbon body, particularly graphite. The graphite body 9 is tension fitted in the electrical insulation 10 sothat a friction seal for mounting the slide contact ring is obtained. In the illustrated embodiment, the nozzles 3a and 4a bounding the contacts 3 and 4 on their end faces, respectively, can also consist of carbon, particularly graphite. For the position of the switching unit shown, the springs 17 press the contact elements 7 against metallic sleeve 9.

FIG. 3 shows a somewhat differently constructed contact arrangement for a compressed-gas circuit breaker according to FIG. 1. Here also, one-half of a longitudinal cross-section is shown. In this embodiment, the slide-contact ring 9 is only partially built as a carbon structure, particularly, a graphite structure. The slide-contact ring is held by friction in a metallic sleeve 9a which in turn is held in the electric insulation 10. The sleeve 9a can be applied by flame-spraying on the outer circumference of the carbon structure. It is also possible to press the carbon structure into the sleeve. It is especially advantageous to couple the metallic sleeve 9a to the contact elements 7 so that in lieu of the electrical connection between the slide-contact ring 9 and the contact elements 7 there is a transition of low resistance.

What is claimed is:

1. A contact arrangement for an electric compressedgas circuit breaker equipped with gas-blast means for blasting a stream of gas through the arc drawn when the breaker opens; the contact arrangement comprising: two stationary contact pieces; a switching unit movable between closed and open positions for electrically bridging said contact pieces in the closed position and for electrically disconnecting said contact pieces in the open position whereby the arc develops when said switching unit is moved to the open position; said switching unit including a supporting body, electrical insulation disposed at said supporting body and made of elastic, yielding material, a slide-contact ring carried by said supporting body and slideably contacting one of said contact pieces in the closed position, said slidecontact ring being made of arc-resistant material and being tension-fixed in said electrical insulation, said insulation being disposed between said supporting body and said ring thereby insulating said ring from said body, said slide-contact ring being configured at least in part as a body of carbon material, a plurality of elongated contact elements disposed in said supporting body for electrically connecting said contact pieces when said switching unit is in the closed position, and spring means for spring loading said contact elements to displace the same into electrically conductive contact with said slide-contact ring as said ring and said contact elements separate from said one contact piece when said switching unit moves into the open position.

2. The electric circuit-breaker of claim 1, said body of carbon material being a body of graphite.

3. The electric circuit-breaker of claim 2, said electrical insulation being made of polytetrafluoroethylene. 

1. A contact arrangement for an electric compressed-gas circuit breaker equipped with gas-blast means for blasting a stream of gas through the arc drawn when the breaker opens; the contact arrangement comprising: two stationary contact pieces; a switching unit movable between closed and open positions for electrically bridging said contact pieces in the closed position and for electrically disconnecting said contact pieces in the open position whereby the arc develops when said switching unit is moved to the open position; said switching unit including a supporting body, electrical insulation disposed at said supporting body and made of elastic, yielding material, a slidecontact ring carried by said supporting body and slideably contacting one of said contact pieces in the closed position, said slide-contact ring being made of arc-resistant material and being tension-fixed in said electrical insulation, said insulation being disposed between said supporting body and said ring thereby insulating said ring from said body, said slidecontact ring being configured at least in part as a body of carbon material, a plurality of elongated contact elements disposed in said supporting body for electrically connecting said contact pieces when said switching unit is in the closed position, and spring means for spring loading said contact elements to displace the same into electrically conductive contact with said slide-contact ring as said ring and said contact elements separate from said one contact piece when said switching unit moves into the open position.
 2. The electric circuit-breaker of claim 1, said body of carbon material being a body of graphite.
 3. The electric circuit-breaker of claim 2, said electrical insulation being configured as a ring-shaped body mounted on said supporting body.
 4. The electric circuit-breaker of claim 1, said slide-contact ring comprising a metallic sleeve, said body of carbon material being held friction-tight in said sleeve, said sleeve being held in said electrical insulation.
 5. The electric circuit-breaker of claim 4, said contact elements being mounted so as to be electrically engageable with said sleeve.
 6. The electric circuit-breaker of claim 1, said electrical insulation being made of polytetrafluoroethylene. 